Abstract

To identify members of the translocation machinery for peroxisomal proteins, we made use of the two-hybrid system to establish a protein linkage map centered around Pex5p from Saccharomyces cerevisiae, the receptor for the C-terminal peroxisomal targeting signal (PTS1). Among the five interaction partners identified, Pex14p was found to be induced under conditions allowing peroxisome proliferation. Deletion of the corresponding gene resulted in the inability of yeast cells to grow on oleate as well as the absence of peroxisomal structures. The PEX14 gene product of approximately 38 kDa was biochemically and ultrastructurally demonstrated to be a peroxisomal membrane protein, despite the lack of a membrane-spanning domain. This protein was shown to interact with itself, with Pex13p and with both PTS receptors, Pex5p and Pex7p, indicating a central function for the import of peroxisomal matrix proteins, either as a docking protein or as a releasing factor at the organellar membrane.